System for amplifying radiant-energy oscillations



June 3, 1930. Q MARVEL 1,761,530

SYSTEM FOR AMPLIFYING RADIANT ENERGY OSCILLATIONS Filed Aug. 23, 1924 5 Sheets-Sheet l Jnwntoz June 3, 1930. o, MARVEL 1,761,530

SYSTEM FOR AMPLIFYING RADIANT ENERGY OSCILLATIONS Filed Aug. 25, 192.4 s Sheets-Sheet 2 a Q I git/m g 3d a s q M li'i R2 & g; Q a V fi n v H June 3, 1930.. Q E; MARVEL 1,761,530

SYSTEM FOR AMPLIFYING RADIANT ENERGY OSCILLATIONS Filed Aug. 23, 1924 5 Sheets-Sheet 5 Patented June 3, 1930 UNITEDSTATES PATENT OFFICE ORIN E. MARVEL, OF DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO GENERAL MOTORS RADIO CORPORATION, OF DAYTON, OHIO, A CORPORATION OF OHIO SYSTEM FOR AMPLIFYING RADIANT-ENERGY OSCILLATIONS Application filed August 23, 1924. Serial No. 733,774.

The present invention relates to the amplifying or receiving and amplifying of radlant cnergy oscillations. More particularly it relates to an apparatus employing electron d1scharge devices of the audion type.

One of the principal objects of the invention is to provide means for increasing the effectiveness of the electron discharge devlces when used for a double purpose.

Another object is to provide circuits and apparatus for utilizing electron discharge devices for amplifying both radio and audio frequency energy oscillations in a more effective manner than has heretofore been accomplished. i I

A still further object resides in the provision of a novel method and means for tuning a receiving apparatus. 7

Further objects of the invention will be apparent from the following description when taken in connection with the accompanying drawings in which:

Fig. 1 is a diagrammatic View illustratlng one form of the present invention; t

Fig. 2 is a diagrammatic view illustratlng a modified form of the invention;

Fig. 3 is a diagrammatic View of a portion of the invention; I

Fig. 4 is a diagrammatic view illustrating the tuning features of the present invention; and

Fig. 5 is a vertical section of the tuner, the fixed capacity being omitted for convenience in illustration.

Referring to Fig. 1, numerals 20, 21 and 22 designate electron discharge devices of the audion type, each having a heated electron discharge cathode or filament 23, a grld or input terminal 24 and a plate or output terminal 25. The electron discharge devices 20 and 21 are herein employed as amplification devices for amplifying both radio and audio frequency energy oscillations. Their filaments 23 are connected in parallel for receiving heating current from the battery source A, one side of the filament being connected to the positive battery conductor 26 and the other side being connected through the common rheostat 27 to the negative battery conductor 28. The electron discharge device 22 is herein employed primarily as a detector for translating radio frequency energy oscillations or signals into audio frequency energy oscillations or signals, its filament 23 being connected to the positive side of the battery A through conductor 20 and to the negative side of the battery A through conductor 30 and rheostat 31.

Connected to the grid or input terminal 24 of the electron discharge device 20 is an input circuit 32, 33 which includes the secondary coil of the adjustable inductively coupled air core transformer or tuner 34. The primary coil of transformer 34 is connected in an antenna circuit 35. Condenser 36 'is connected in the input circuit 32, 33 in parallel with the secondary of transformer 34, this condenser being preferably variable whereby the input circuit 32, 33 may be tuned or made resonant to a desired radio frequency oscillation to be impressed upon it.

A plurality of output circuits are connected with the plate or output terminal 25 of the first discharge device 20. One of these output circuits may be traced from plate 25 through conductor 37, condenser 38, the primary of air core transformer 39 and conductor 40 to a negative conductor 28, and thence to the negative side of the filament 23 of discharge device 20. Owing to the presence of condenser 38 this output circuit is largely opaque to audio frequency oscillations but will permit the passage of radio frequency oscillations, and it is therefore referred to as a radio frequency output circuit. A second output circuit is taken off the conductor 37 between the plate 25 and the condenser 38 and may be traced from plate 25 through conductor 41, electrical translating device or telephone 42 and battery B to the negative conductor 28 and thence to the negative side of filament 23 of discharge device 20. Owing to the high blocking impedance of the telephone 42, this last-mentioned output circuit is largely opaque to radio frequency oscillations, but as it freely passes audio frequency oscillations it is for convenience termed an audio frequency output circuit. The battery B establishes a definite potential difference between the plate 25 and the filament 23. The

grid 24 preferably has a negative bias with respect to the filament 23, that is to say, the potential of the grid 24 is negative with respect to the filament 23. As is well understood, the radio frequency oscillations impressed upon the input or grid circuit 32, 33 result in variations in the potential of grid 24, and these variations in grid potential result in variations in the plate similar to those in the grid circuit. These variations having been produced by a local source of current B may be, and in the present instance are, stronger than the received'oscillation. The grid or input circuit 32, 33 thus controls and initiates variations of radio frequency in step therewith in the plate. Owing to the high impedance of the audio frequency circuit, such amplified radio frequency oscillations pass through the radio frequency output circuit to the primary coil of air core transformer 39 and are impressed upon the tuned input circuit 43, 44 of the second discharge device 21, and this input circuit having a variable condenser 45 in parallel with the secondary coil of the air core transformer 39.

The second discharge device 21, like the discharge device 20, is provided with two output circuits, one being a radio frequency output circuit and the other being an audio frequency output circuit. The radio frequency circuit may be traced from the plate or output terminal 25. through the conductor 46, condenser 47 air core transformer 48 and conductor 49 to the negative conductor 28 and thence to the negative side offilament 23 of discharge device 21. The audio frequency output circuit takes off from the conductor 46 between plate 25 and condenser 47 and may be traced from plate 25 through "conductor 50, primary coil of audio frequency transformer 51, conductor 52 and battery B to the negative conductor 28 and thence to the negative side of filament 23 of discharge device 21. A condenser 59 is connected across the terminals of battery B. The operation of the discharge device 21 is similar to that of the first discharge device 20, that is, the radio frequency oscillations impressed upon the tuned input circuit 43, 44 control and initiate similar radio frequency oscillations in the plate of the discharge device 21. The high impedance of the transformer 51 in the audio frequency output circuit 50, 52 of the discharge device 21 blocks the radio frequency oscillations and causes the latter to pass through the radio frequency output circuit and hence through the primary windings of the auto transformer 48, which in turn impresses amplified radio frequency oscillations upon the tuned input circuit 53, 49 of the third discharge device 22, said inputcircuit including a variable condenser 54 connected between the conductors 49 and 53.

Voltage is impressed upon the plate 25 of the third discharge device 22 from a local source of energy through the audio frequency output circuit which may be traced from plate 25 through conductor 55, primary coil of audio frequency transformer 56 and conductor 57 to the positive terminal of battery B, the negative side of which is connected through negative conductor28 to the negative side of filament 23 of the discharge device 22. A condenser 58 is connected between the con ductor 55 and conductor 30, which latter is connected with the negative conductor 28.

As already stated, the third discharge device 22 is herein employed primarily as a detector, that is, by properly controlling the relative potential of its electrodes 23, 24 and 25 in accordance with the characteristic curves of the discharge device 22, groups of radio frequency oscillations impressed upon the input circuit may be so rectified or integrated that oscillations of group or audio frequency are initiated in the output circuit of the discharge device 22. Such audio frequency oscillations pass through the return conductor of the audio frequency output circuit 55, 57 to the primary coil of the audio frequency transformer 56, the secondary coil of which is connected in the conductor 44, forming part of the input'circuit 43, 44 of the discharge device 21. The audio frequency oscillations from the third discharge device or detector 22 are thus impressed upon the input circuit of the second discharge device or amplifier 21, and such audio frequency oscillations control and initiate similar amplified audio frequency oscillations in the plate 25 of the second discharge device 21. The amplified audio frequency oscillations initiated in the plate of the second discharge device 21 pass through the return conductor of the audio frequency output circuit 50, 52 and are impressed by means of the audio frequency transformer 51 upon the input circuit 32, 33 of the first discharge device or amplifier 20. Further amplified audio frequency oscillations are thus initiated in the first discharge device 20 and such oscillations pass through the audio frequency output circuit 41 to the electrical translating device such as a telephone 42 where they may be heard by the operator.

From the foregoing, it will be observed that the discharge devices 20, 21 and 22 are arranged in a series, or in cascade, in the order mentioned. Radio frequency oscillations impressed upon the first amplifying device21) initiate greatly amplified radio frequency oscillations which are then impressed upon the second amplifying device 21. The second amplifying device 21 is thus more heavily loaded, as regards radio frequency energy oscillation, than the first device 20. Audio frequency oscillations coming from the detector 22 are first impressed upon the second-amplifying device 21, and the amplified audio frequency oscillations initiated in this device are then impressed upon the first amplifying device 20. Thus the first amplifying device 20 carries a relatively large audio frequency load and a small radio frequency load, and the second amplifying device 21 carries a relatively large radio frequency load and a small audio frequency load. The advantage of this arrangement is that the load on the amplifying devices 20 and 21 may be more nearly equalized, with the consequences that better results are obtainableand the capacity of the receiving apparatus, as regards amplification, is greatly increased.

A novel feature of the present invention is the arrangement by which each amplifying device is provided with a pair of output circuits both of which are controlled by a single input circuit and which are so constructed and arranged that radio frequency oscillations pass through one of the output circuits and audio frequency oscillations pass through the other output circuit, each of said output circuits being largely opaque to oscillation of the frequencies which pass through the other output circuit. It will be observed that by this arrangement the current from the local battery for the plate does not pass through the primary windings of the air core or radio transformer connected with the plate.

Another feature of the present invention is that the secondary coils of audio frequency transformers 51 and 56 which are in the input circuits of the amplifying devices 20 and 21, are so constructed and arranged as to provide a distributed capacity adequate for the passage therethrough of the radio frequency energy oscillations impressed upon the said input circuits. The distributed capacity of the secondary coils of the transformers 51 and 56 is indicated by dotted lines 60 and 61 respectively. An advantage of this feature is that it becomes unnecessary to provide external capacity or condensers around the audio frequency transformers 51 and 56. Further, the herein described arrangement of audio transformer in the input circuit has the desirable effect of causing a potential bias of the grid, relative to the filament.

The form of receiving apparatus shown in Fig. 2 is similar in its general construction and operation to the IQCGlXillQ apparatus shown in Fig. 1. However, instead of amplifying both radio and audio frequency oscillations in the discharge device 20 as in Fig. 1, the electron discharge device 20 is employed only for the amplification of radio frequency oscillations and a separate electron discharge device 80 is provided for amplifying the oscillations or groups of OSClllations of audio frequency coming from the discharge device 21. Referring now particularly to Fig. 2, it will be observed that such oscillations from thedischarge device 21 flow through the return circuit 50, 52 and are impressed by means of audio frequency transformer 81 upon the input circuit 82 of the discharge or amplifying device 80. A telephone 83 or other form of electrical detecting device is connected in the output circuit 84 of the discharge device 80. In this form of the invention the conductor 41 which maintains the plate 25 of discharge device 20 at the desired positive potential is provided with a choke coil 85 to block the passage of radio frequency oscillations through the branch conductor 41.

It has been discovered that by providing the air core transformer or tuner 34 with a condenser of fixed capacity connected bethe secondary winding and the ground connection of the primary winding, as shown diagrammatically at 101 in Fig. 1, novel characteristics are imparted to the tuner and that quite extraordinary results are obtainable in the tuning and operation of the receiving set. In radio receiving sets of the type heretofore known having a tuner and one or more tuned circuits connected in cascade, it is well understood that the adjustment of the capacity or inductance of the.

first tuned circuit varies according to the characteristics of the antenna circuit in which the primary winding of the tuner may be connected. That is to say, if it is assumed that a variable condenser is employed for tuning the first tuned circuit then the adjustment or setting thereof for tuning the circuit. to receive a predetermined oscillation, of say 380 meters wave length, will be the same when the receiver is connected with different antennae only if the fundamental characteristics of the several antenna circuits are the same. Since it is not practicable to construct all antenna circuits of uniform or standard characteristics, it is apparent that the setting of the variable condenser in the first tuned circuit of previous forms of construction will necessarily be different in different installations and that this setting will seldom, if ever, agree with the setting of the similarly arranged variable condensers in the succeeding tuned circuits of the receiving set.

According to the present invention, on the other hand, receiving sets constructed so that the variable condensers of the several tuned circuits have identical settings when the set is connected with an antenna circuit having what is herein termed a standard predetermined fundamental wave length, may be connected in other antenna circuits differing Widely in characteristics from the standard antenna referred to, and the set may be adjusted so that the settings of the several condensers in the several tuned circuits are still substantially the same. Moreover, receiving sets of identical construction, when connected in antenna circuits of different characteristics, may be so adjusted that the settings of the variable condensers of one receiving set are the same as the settings of the Variable condensers in other receiving sets when the sets are tuned to receive oscillations of a given wave length.

It will be apparent from the above description that antenna circuits of varying characteristics may be thus reduced to antenna circuits of standard or fundamental wave length when connected with receiving sets constructed according to the present invention. This is of great practical value in overcoming one of the principal disadvantages of known receiving sets, namely, the burden placed upon the user of having to calibrate, at the expense of great loss of time, the variable condenser of at least the first tuned circuit for the particular antenna in which the receiver is connected.

The present invention makes it feasible to manufacture receiving sets of standard construction which may be sold generally for connection in antenna circuits of varying characteristics (and to accompany such receiving sets with a log or table of standard condenser settings), since the user may readily transform his antenna circuit, when connected with the receiving set, to one of the standard predetermined fundamental characteristics and thereafter at once receive radio signals of any desired frequency merely by setting the several variable condensers at the corresponding predetermined values given in the log or table accompanying the receiving set.

In order to facilitate the understanding of the operation of the tuning features of the present invention and the novel results obtained thereby, a general outline of the theory of operation is given herewith in so far as it is now understood, reference being made for this purpose to Fig. 3 of the drawings. In this figure as well as in Figs. 4 and 5 the various parts have been given the same refererence characters as the corresponding parts in Figs. 1 and 2. Referring now to Fig. 3, the primary and secondary windings of the variable air core transformer or tuner 34 aredesignated by reference characters 102 and 103 respectively, it being understood that the primary and secondary windings are inductively coupled. The antenna circuit having therein the primary winding 102 may be indicated as a closed circuit or loop 35, the capacity of the antenna circuit-beingindicated by the condenser Ca. The capacity of the variable condenser 36 of the first tuned circuit is indicated as Cg, and the capacity of the fixed condenser 101 is taken as Cc. Since the primary and secondary windings of the tuner 34 are inductively connected, the have a capacity which is here indicated as t and sincethis capacity may be varied, as will be hereinafter more fully explained, merely by moving primary and secondary windings rotatable with respect to one another this capacity Ct is indicated as variable. The designated capacity Ct is indicated as effective across the two coils 102 and 103 at the ends of these windings so that one theory of operation of the device may be more readily explained, but as a matter-of-fact the capacity Ct may be really effectively distributed along the lengths of the coils. However, due to the presence of the condenser C0 the effective capacity Ct is probably the equivalent of a condenser connected at some point between the middle and the ends of the two coils 102 and 103. It will be apparent from Fig. 3 that the capacities Ct, Ca and C0 are in series with one another and in parallel with the inductance or secondary winding 103 of the first tuned circuit, and likewise that the capacity Cg is in parallel with the inductance 103. Assuming that capacity Ca is fixed and is that of the selected standard antenna circuit it is apparent that the first tuned circuit 32, 33, may be tuned to the desired frequency either by adjusting the variable capacity Cg or by changing the relative positions of the windings 102 and 103 to adjust the variable capacity Ct. Having constructed the receiving set so that the variable condenser 36 of the first tuned circuit, when connected with a standard antenna circuit, has the same reading as the variable condensers of the succeeding tuned circuits, as indicated in Fig. 4, it is apparent that when the receiving set is connected in a difierent antenna circuit having a different value for C0, the first tuned circuit 32, 33 is no longer properly tuned for the desired frequency above-mentioned. But instead of resetting the variable condenser 36 of the first circuit, as has been the practice in known forms of receiving apparatus, the condenser 36 may be retained at the same reading. as it had when Ca was standard, and the first tuned circuit 32, 33 may be tuned by varying the relative position of the tuner windings and hence the capacity Ct. With this adjustment of the tuner windings 102 and 103 and the corresponding value of Ct which it thereby establishes, the antenna as now connected with the receiving set has substantially the electrical properties of said standard antenna. Therefore further tuning of the receiving set may be effected by merely setting the condenser dials 36, 45 and 54 identically in accordance with the log or table accompanying the receiving set, which log may be standard and uniform for all receiving sets.

In so far as the present invention is now understood, this novel method of tuning may be attributed to the connection of the condenser 101 between the inductively coupled windings 102 and 103 of the tuner 34. It appears that introduction of this capacity so influences the action of the tuner windings that the capacity between them becomes variable, this capacity depending for its exact value upon the relative positions of the tuner windings. In this respect the present invention provides a tuner having novel electrical characteristics. The antenna circuit is aperiodic in nature by reason of the absence of extra condensers in series or parallel with the coil 102, and adjustments of the condenser 36 in tuning the grid circuit of the first tube will therefore have no effect towards tuning the antenna circuit. The amount of capacity of the antenna circuit which is effective on the secondary coil 103 and the circuit to which it is connected is controlled by adjusting the relationship of the two coils 102 and 103 in such a manner as to properly tune the secondary circuit. The inductance of the coil 103 in this secondary circuit is therefore of such a nature that it will properly cooperate with the total capacity effective in this secondary circuit so as to tune the same. It will thus be apparent that although some of the capacity of the primary circuit is at all times reduced and effective in the secondary circuit the amount of this capacity which is thus transferred to the secondary circuit is controlled to properly permit the tuning of this circuit.

From the foregoing it will be perceived that the present invention provides a novel method of tuning receiving sets. The variable condensers of the several tuned circuits may be adjusted to substantially identical settings as indicated in Fig. 4 which illustrates the settings for a receiver having three variable condensers 36, 45 and 54; in three tuned circuits, which condensers may correspond to the similarly numbered condensers of Fig. 1. From the log or table accompanying the receiving set it may be determined that to tune the circuits to a frequency of say 380 meters the several condensers should be set at 33. The tuner 34 is then adjusted by moving the windings 102 and 103 relative to one another until the clearest and loudest signals are obtained. The antenna circuit now corresponds to the standard antenna circuit of predetermined fundamental wave length and the tuner 341 may be left in its adjusted position tuning to other frequencies being effected merely by setting the condensers to the positions indicated on the log or table, it being understood that all the variable condensers have substantially the same reading. The receiving set being tuned in accordance with the method given above and receiving signals of the desired Wave lengths, it may be desirable at times to further slightly adjust either the tuner 34 or the condenser 36 to either strengthen or clarify the signals which are being received, or in some cases, owing to the extreme loudness of the signal, the operator may so adjust the tuner 34 to reduce the intensity of the signal.

For the purpose of completing the disclosure of the invention, and to facilitate its practical application by those skilled in the art, there is illustrated in Fig. 5 a sectional View of the preferred form of tuner, the fixed condenser 101 being omitted for convenience in illustration. The secondary coil is rigidly mounted on panel 104 by means of a suitable bracket 105. The primary coil 102 is mounted on shaft 106 and is capable of being rotated within the secondary coil 103 by means of knob 107 to obtain different degrees of coupling, selectivity, and tuning. It has been found that very satisfactory results may be obtained in receiving signals of frequency varying from 210 meters to 600 meters by the use of a tuner of the form herein illustrated, the primary winding consisting of 20' turns of No. 27 B. & S. gauge double silk copper wire wound on an insulated tube 2% inches in diameter having an inductance of about 100 microhenrys, and the secondary winding consisting of 63 turns of N o. 27 B. & S. gauge double silk copper wire wound on an insulated tube of 3 inch diameter and having an inductance of approximately 345 microhenrys. The fixed condenser 101 preferably has a value of .00001 microfarad, and the antenna may vary in length from about 20 feet to 300 feet, the corresponding capacities of the antenna circuit varying from about .00008 microfarad to .0007 microfarad. The variable condenser 36 employedin the first tuned circuit may have a capacity varying froma minimum of about .00005 microfarad to a maximum of about .0003 microfarad. It will, of course, be understood that a considerable variation may be made in the size, proportion and constants of the apparatus herein described provided they are properly co-related with respect to each other, but these specific figures are given so that anyone skilled in the art can immediately set up the apparatus and practice the invention.

\Vhile a practice has grown up in the art, of considering oscillations above fifty thousand cycles per second as radio frequency oscillations, and those below fifty thousand cycles per second as audio frequency oscillations, it should be understood that there is no sharp dividing line between radio and audio frequency oscillations and that where the terms audio frequency oscillations and radio frequency oscillations, and audio'frequency clrcuits and radio frequency circuits are employed in the specification and claim, it is not intended that these terms should be limited to oscillations of any definite number of vi brations per second. It should be understood that radio frequencies may at times include the so-called intermediate frequencies and the so-called audio frequencies include frequencies extending above the range of audibility of the human ear, and that'the true dividing line should, therefore, be considered as the number of cycles which when impressed upon a given circuit will accomplish the desired result, as herein disclosed.

While the invention herein disclosed has been illustrated in its application for the receiving and translating of radiant energy oscillations, it should be expressly understood that the invention is not necessarily limited to use in receiving apparatus but may find application to equal advantage in transmitting apparatus. Likewise it should be understood that while the transformer 34 is herein described as connected between the antenna circuit and the first tuned circuit, that is, between the first and second circuits of the receiving and relaying apparatus, it is not limited in its application to these particular circuits, but that the principal of the tuner or transformer 34 together with it's.

novel characteristics may be employed in other relations than the one illustrated.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made in either without departing from the scope of the invention which is defined in the appended claim.

What is claimed is:

In a receiving apparatus for receiving oscillations of radiant energy, an aperiodic antenna receiving circuit for receiving radiant energy oscillations, said circuit bein connected to ground, an air core trans ormer having variably coupled inductively connected primary and secondary coils, said primary coil being connected in the antenna circuit, means for relatively varying said coils, and a condenser connected at one side to said secondary coil and at the other side to the grounded connection of said primary coil.

In testimony whereof I hereto afix my signature.

ORIN E. MARVEL. 

